The newly diagnosed RA and RA MTX-treated groups were more likely to have elevated IL-40 levels than healthy subjects, independent of age and gender in the logistic regression analysis (OR = 1.023, 95% CI: 1.010–1.035, p = 0.002; OR = 1.023, 95% CI: 1.011–1.036, p < 0.001, respectively). Here, C17orf99 is linked to rheumatoid arthritis.